While a mobile device having a touch panel mounted on a front surface of a display device is in the wide market at the present, the touch panel mainly comes in a resistive type touch panel and a capacitive type touch panel. According to the resistive type touch panel, a movable plate and a support substrate are laminated with a slight insulation space left between the movable plate and the support substrate such that conductor layers formed on their opposed surfaces are separated from each other, and when the movable plate is pressed, the fact that the conductor layers are brought into contact with each other at the pressed position is electrically detected, and pressed position data representing the pressed position is outputted to an arithmetic processing unit. Meanwhile, according to the capacitive type touch panel, a position is detected by detecting a change in electrostatic capacity between a fingertip and a conductive film.
(1) According to the resistive type touch panel, as described above, since the movable plate and the support substrate have the laminated structure in which they are arranged with the slight insulation space left between them, pressed stroke to the movable plate is extremely small such as 0.01 to 0.5 mm, so that it is difficult for the operator to feel input operational feeling. In addition, as for the capacitive type, since the pressed stroke does not exist, the operator cannot feel the input operational feeling.
Thus, progress has been made on a tactile feedback type touch panel in which a vibration is generated from a simple drive circuit so as to be detected by an operator when an input operation surface is pressed, and felt by a pressing finger. For example, according to a patent literature 1, a piezoelectric substrate (vibration element) having a pair of drive electrodes (piezoelectric elements) adhered to opposed both surfaces is adhered to a movable plate or a support substrate directly or through the drive electrode, and when pressing to an input operation surface is detected, a drive voltage is applied to the pair of drive electrodes, and the movable plate or the support substrate is vibrated due to expansion and contraction of the piezoelectric substrate (vibration element).
(2) In addition, the mobile device is provided with a function to reproduce sound in general, but a cone-shaped speaker 800 is mounted in a casing 202 as a component separated from the above-described touch panel 204 (refer to FIG. 18). In this case, sound directionality is too high because movement of a vibration plate of the cone-shaped speaker 80 is constant, and there is a problem that the sound cannot be caught unless an ear is completely put to a hole 81. In addition, there are other problems that dust-proofness and water-proofness are poor because protection is provided with the mesh 81 such that the sound generated from the speaker 80 is not hindered, and there is a limit in design due to a mount design in consideration of the speaker 80.
Thus, the applicant has attempted to solve the problem by activating the touch panel as a speaker. That is, an audio output is generated by adhering the piezoelectric substrate having the pair of drive electrodes adhered to the opposed both surfaces to the movable plate or the support substrate of the touch panel directly or through the drive electrode, and applying the drive voltage to the pair of drive electrodes to vibrate the movable plate or the support substrate so as to execute the expansion and contraction of the piezoelectric substrate.
(3) By the way, use conditions of the mobile device is stricter than that of a device set in an office, and certain levels of impact resistance, dust-proofness, and drip-proofness are required because the mobile device could fall, or water droplets could be put on the mobile device.
Therefore, as shown in a patent literature 2, an elastic member frame is mounted on an outer periphery of a touch panel, and the mobile device is hermetically sealed when the elastic member frame (gasket) is pressed against a casing which covers an upper surface periphery of the touch panel in the shape of a frame, so that dust-proofing and water proofing functions and an impact resistance function are realized.    Patent Literature 1: Japanese Unexamined Patent Publication No. 2003-122507    Patent Literature 2: Japanese Unexamined Patent Publication No. 11-74661